Montana State University

Research by MSU alumnus featured at solar conference

July 10, 2013 -- MSU News Service

Henry “Trae” Winter, who received his doctorate in 2009 from MSU, spoke about coronal loops, such as this one, during a video briefing from MSU. (Image courtesy SDO/NASA).    High-Res Available

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MSU News Service
Tel: (406) 994-4571

BOZEMAN – A solar physicist who earned his doctorate at Montana State University and is now an astrophysicist at the Harvard-Smithsonian Center for Astrophysics was one of three researchers whose work was featured July 9 during a video briefing from MSU.

Henry “Trae” Winter, who said his return to MSU was like a huge homecoming, presented his research about coronal loops at the summer meeting of the Solar Physics Division of the American Astronomical Society. The meeting that brought solar physicists from around the world to MSU began July 8 and ends July 11.

Winter’s study was titled, “The Problem with Coronal Loops.” During a video briefing from the Strand Union Building, Winter said he and his collaborators had solved a 21-year-old mystery about the sun. They discovered that an optical illusion in the best images of the sun caused scientists to believe that coronal loops are a constant width, like strands of rope. However, the loops are actually tapered, wider at the top and narrower at the ends. This finding has important implications for coronal heating.

“You need less energy to heat the corona if the loops have a tapered geometry, which is exactly what we found,” Winter said.

The sun’s outer atmosphere, or corona, has posed an enduring mystery. Why is it so hot? The sun’s visible surface is only 10,000 degrees Fahrenheit, but as you move outward the temperature shoots up to millions of degrees. It’s like a campfire that feels hotter the farther away you stand.

To understand how the corona is heated, solar physicists study coronal loops. These structures are shaped like an upside-down U and show where magnetic field lines are funneling solar gases or plasma.

Winter and his colleagues constructed a computer model of a tapered loop using basic physics. Then they processed their model to show how it would look when photographed by instruments like the Atmospheric Imaging Assembly, a collection of high-resolution coronal telescopes onboard NASA’s Solar Dynamic Observatory.

They found that even the best available images wouldn’t have the resolution to show the loop’s true structure. As a result, a tapered loop would appear tubular even though it wasn’t.

“In science we always compare theory to reality. But if your view of reality is incorrect, your theory will be wrong too. What we thought we saw could be just an effect of the instrument,” Winter explained.

The team’s work shows that better instruments with higher resolution are still needed to reveal the true shape and structure of the loops.

“Coronal loops are like Russian nesting dolls. We keep pulling them apart but we haven’t gotten to the smallest one yet,” Winter said.

Winter’s co-authors on the study were Chester Curme of Boston University, Katharine Reeves from the Harvard-Smithsonian Center for Astrophysics and Petrus Martens of MSU.

Martens was also Winter’s thesis adviser when Winter was working on his doctorate at MSU. Winter spent 6 ½ years at MSU, earned his doctorate in 2009, then joined the Harvard-Smithsonian Center for Astrophysics. Martens and Winter have continued to collaborate after Winter’s graduation.

“MSU has really distinguished itself for producing solar physicists who have done very well in the field,” Winter said. “I feel very honored that I’m a part of them.”

Martens said the fact that Winter was featured at the video briefing was “another feather in the cap for MSU.” He noted that the simulations in Winter’s paper were conducted with a code that Winters developed while he was a graduate student at MSU. The research project he presented was started while Winter was still at MSU.

Martens also noted that Curme is an undergraduate involved in the Research Experience for Undergraduates (REU) program at the Smithsonian Astrophysical Observatory – “The kind of student involvement we want more of here at MSU.”


Evelyn Boswell, (406) 994-5135 or